The build-up of sand and earthen materials at the well bottom and deposits of paraffin and or asphalt inside the well casing cause persistent problems for producing gas and oil wells. It is necessary to remove these foreign materials periodically to maintain well output. This need has long been present in the oil field, and various prior art well cleaning devices have been offered in response. Prior art devices for cleaning and flushing undesirable materials from a well casing or well bore by fluid flow are well known. In the prior art as well as in the present invention, the general term “fluid” is construed to represent either a liquid or a gaseous medium. In actuality, prior art devices in general are designed to operate with relatively incompressible liquid media, but can work with expansible gaseous media, which behave quite differently from liquids. In all cases, ambient pressure in the hole is the controlling variable. As a point of reference, the bottom hole pressure in a typical oil or gas well may be 3,000 to 4,000 p.s.i. When the operating pressure of the cleaning device significantly exceeds the downhole pressure, circulating fluid will be lost into the surrounding formation.
H. M. Green, U.S. Pat. No. 1,279,333 discloses a well cleaning device comprising a tubular member having a threaded upper end for connection to the pump tubing and a conical lower end to assist in advancing through the well bottom materials as they are removed. Water jets are arranged in a spiral pattern on the tubular member and directed tangentially in order to maintain a vigorous whirling action for sand removal. Green teaches that the lowermost jets are directed downwardly, intermediate jets are directed tangentially and uppermost jets are directed upwardly. Green does not teach the use of upwardly directed jets to create a low pressure zone, nor the application of differential pressure for extraction of entrained solids from a lower level.
F. F. Lewis, U.S. Pat. No. 2,771,141 discloses a well bore cleaning device using upwardly directed jets, which is intended to preform the function of mechanical “scratchers” on the casing exterior. The jets direct a fluid to impinge upon the well bore walls to dislodge filter cake or mud deposits and flush them up the bore. Suitable fluids may include cutting acids or solvents. Lewis does not teach the use of upwardly directed jets to create a low pressure zone above the scouring area with a gaseous medium, nor the application of differential pressure for extraction of entrained solids from a lower level of the well.
D. Robichaux, U.S. Pat. No. 3,912,173 discloses a formation flushing tool having plurality of longitudinally connected sections, each section with jetting holes for a fluid such as water pointed in a particular direction unique to that section. In the disclosed embodiment, the jets are directed downward in the lower section, horizontally outward in the intermediate section, and upward in the top section. The tubing inside diameter is reduced successively from each section down to the next, so that a suitably sized plug may be dropped in to shut off fluid flow at a selected level. In this manner, only those jets above the plug are selected to be active. Robichaux does not teach the use of upwardly directed jets to create a low pressure zone above the scouring area with a gaseous medium, nor the application of differential pressure for extraction of entrained solids from a lower level of the well.
A first object of the present inventions is therefore, to provide apparatus for cleaning and flushing wells, which is specifically adapted to utilize gases and take advantage of the expansible nature of gases for lifting materials in the annulus. A second object is to accomplish this in apparatus that can clean efficiently at operating pressures not greatly in excess of the bottom hole well pressure. A third object is to accomplish this in apparatus that is durable and not susceptible to damage. Yet another object is to provide this apparatus in a form that can be used in either rotating or non-rotating strings.